U.S. patent application number 13/751399 was filed with the patent office on 2014-07-31 for fluid distribution and mixing grid for mixing gases.
This patent application is currently assigned to ALSTOM TECHNOLOGY LTD. The applicant listed for this patent is ALSTOM Technology Ltd. Invention is credited to Yen-Ming Chen, Mitchell B. Cohen, Armand A. Levasseur.
Application Number | 20140208994 13/751399 |
Document ID | / |
Family ID | 50000896 |
Filed Date | 2014-07-31 |
United States Patent
Application |
20140208994 |
Kind Code |
A1 |
Cohen; Mitchell B. ; et
al. |
July 31, 2014 |
FLUID DISTRIBUTION AND MIXING GRID FOR MIXING GASES
Abstract
A grid for distributing and mixing fluids in a duct includes a
plurality of lances arranged in a first plane and configured to be
positioned transverse to a direction of a first fluid flowing
outside of the lances and within a predetermined flow area. Each of
the plurality of lances has at least one first inlet and a
plurality of outlet nozzles. One or more of the outlet nozzles is
directed generally in the flow direction of the first fluid outside
of the lances, and is configured to discharge a second fluid
therefrom.
Inventors: |
Cohen; Mitchell B.; (West
Hartford, CT) ; Chen; Yen-Ming; (Broad Brook, CT)
; Levasseur; Armand A.; (Windsor Locks, CT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ALSTOM Technology Ltd |
Baden |
|
CH |
|
|
Assignee: |
ALSTOM TECHNOLOGY LTD
Baden
CH
|
Family ID: |
50000896 |
Appl. No.: |
13/751399 |
Filed: |
January 28, 2013 |
Current U.S.
Class: |
110/205 ;
110/215; 110/216; 110/303 |
Current CPC
Class: |
F23C 9/00 20130101; Y02E
20/344 20130101; Y02E 20/322 20130101; Y02E 20/32 20130101; B01F
3/02 20130101; F23L 7/007 20130101; Y02E 20/34 20130101; F23J 15/02
20130101; F23L 2900/07001 20130101; B01F 5/0463 20130101; F23J
15/022 20130101; B01F 5/0456 20130101 |
Class at
Publication: |
110/205 ;
110/303; 110/215; 110/216 |
International
Class: |
F23L 7/00 20060101
F23L007/00; F23J 15/02 20060101 F23J015/02; F23L 9/00 20060101
F23L009/00; F23C 9/00 20060101 F23C009/00; F23L 15/00 20060101
F23L015/00 |
Goverment Interests
GOVERNMENT RIGHTS
[0001] This invention was made with government support under U.S.
Contract No. DE-NT0005290. The U.S. government holds certain rights
in this invention.
Claims
1. A distribution and mixing grid for mixing fluids in a duct
comprising: a plurality of lances arranged in a first plane and
configured to be positioned transverse to a direction of a first
fluid flowing outside of the lances and within a predetermined flow
area; each of the plurality of lances having at least one first
inlet and a plurality of outlet nozzles; and at least one of the
outlet nozzles being directed generally in the flow direction of
the first fluid flowing outside of the lances, and configured to
discharge a second fluid therefrom.
2. The distribution and mixing grid of claim 1, wherein the
plurality of lances includes a predetermined number of lances
selected to create at a homogeneity of the first fluid and the
second fluid of less than a 0.05 coefficient of variation at a
second plane downstream of the plurality of lances; and the second
plane being spaced apart from the first plane by a first distance
of less than one times a diameter of the flow area.
3. The distribution and mixing grid of claim 1, wherein the
plurality of lances includes a predetermined number of lances
selected to create a homogeneity of first fluid and the second
fluid of less than a 0.02 coefficient of variation at a third plane
downstream of the plurality of lances; and the third plane being
spaced apart from the first plane by a second distance of less than
four times a diameter of the flow area.
4. The distribution and mixing grid of claim 1, wherein the
plurality of lances includes a predetermined number of lances
selected to create at least one target region of concentration of
the second fluid in the first fluid, second fluid having a
concentration of about 21 percent to about 23.5 percent, by weight,
in the target region; the at least one target region being located
at a second plane downstream of the plurality of lances; and the
second plane being spaced apart from the first plane by a first
distance equal to about one times a diameter of the flow area.
5. The distribution and mixing grid of claim 4, wherein the at
least one target region occupies greater than 57 percent of the
flow area.
6. The distribution and mixing grid of claim 1, wherein the
plurality of lances includes a predetermined number of lances
selected to create at least one target region of concentration of
the second fluid in the first fluid, the second fluid having a
concentration of about 21 percent to about 23.5 percent, by weight,
in the target region; the at least one target region being located
at a fourth plane downstream of the plurality of lances; and the
fourth plane being spaced apart from the first plane by a third
distance equal to about two times a diameter of the flow area.
7. The distribution and mixing grid of claim 6, wherein the at
least one target region occupies greater than 89 percent of the
flow area.
8. The distribution and mixing grid of claim 1, wherein the
plurality of lances includes a predetermined number of lances
selected to create at least one target region of concentration of
the second fluid in the first fluid, the second fluid having a
concentration of about 21 percent to about 23.5 percent, by weight,
in the target region; the at least one target region being located
at a fifth plane downstream of the plurality of lances; and the
fifth plane being spaced apart from the first plane by a fifth
distance equal to about three times a diameter of the flow
area.
9. The distribution and mixing grid of claim 8, wherein the at
least one target region occupies greater than 99 percent of the
flow area.
10. The distribution and mixing grid of claim 1, wherein the first
plane is positioned substantially perpendicular to the direction of
the first fluid flowing outside of the lances.
11. The distribution and mixing grid of claim 1, wherein at least
one of the plurality of lances comprises: a first section having a
first inlet and a first closed end; a second section having a
second inlet and a second closed end; and the first closed and the
second closed end being positioned proximate one another.
12. The distribution and mixing grid of claim 13, further
comprising a sleeve, the first closed end and the second closed end
being moveably positioned in opposing ends of the sleeve.
13. The distribution and mixing grid of claim 1, further comprising
at least one flow control device in communication with at least one
of the plurality of lances.
14. The distribution and mixing grid of claim 1, further comprising
a control system in communication with the at least one control
device for controlling flow of the first gas into the at least one
of the plurality of lances.
15. The distribution and mixing grid of claim 1, wherein at least
one of the plurality of lances has at least one of the nozzles
positioned at an angle of about 30 to about 60 degrees, relative to
the direction of the first fluid flowing outside of the lances.
16. The distribution and mixing grid of claim 1, wherein at least
one of the plurality of lances has at least one of the nozzles
positioned at an angle of about 12.5 to about 32.5 degrees,
relative to the direction of the first fluid flowing outside of the
lances.
17. An oxy-combustion system comprising: a furnace defining an
interior combustion area; an oxygen supply system; a fuel supply
system defining a primary flue gas inlet and a fuel outlet; at
least one flue gas processing system positioned downstream of and
in communication with the furnace; a primary gas system defining a
primary flue gas outlet, the primary gas system being in
communication with the at least one flue gas processing system and
the primary flue gas outlet being in fluid communication with the
fuel inlet; a secondary gas system defining a secondary flue gas
outlet, the secondary gas system being in communication with the at
least one flue gas processing system and the secondary flue gas
outlet being in communication with the furnace; the at least one
oxygen discharge line being in communication with at least one of
the primary gas system and the secondary gas system; and a grid
positioned in a duct of at least one of the primary gas system and
the secondary gas system, the grid comprising: a plurality of
lances arranged in a first plane and positioned transverse to a
flow direction of a flue gas outside of the lances and within a
predetermined flow area; each of the plurality of lances having at
least one oxygen inlet and a plurality of outlet nozzles, the
oxygen inlet being in communication with the oxygen supply system;
and at least one of the outlet nozzles being directed generally in
the flow direction of the of flue gas outside of the lances, and
configured to discharge oxygen therefrom.
18. The oxy-combustion system of claim 17, wherein the primary gas
system is in communication with at least one of the furnace, an air
preheater, a particulate removal system, a sulfur removal system, a
flue gas cooler and a carbon dioxide removal system.
19. The oxy-combustion system of claim 17, wherein the secondary
gas system is in communication with at least one of an air
preheater, a particulate removal system, a sulfur removal system, a
flue gas cooler and a carbon dioxide removal system.
20. The oxy-combustion system of claim 17, further comprising an
air preheater in communication with the primary gas system and the
secondary gas system, wherein the grid is positioned at least one
of upstream of the air preheater and downstream of the air
preheater.
Description
TECHNICAL FIELD
[0002] The present disclosure is generally directed to a
distribution and mixing grid, and in particular to an oxygen
distribution and mixing grid for use in an oxy-combustion system
for providing a uniform mixing of oxygen in a flue gas duct.
BACKGROUND
[0003] Steam generators, particularly those of the coal fired type,
can generate harmful emissions. Recent efforts have focused on
oxygen firing (e.g., oxy-combustion) which injects oxygen into a
duct that transports flue gas into a fuel supply system (e.g., coal
pulverizer system) and/or the steam generator. The oxygen can be
supplied from an air separation unit. Due to the elimination of the
inherent nitrogen that occurs with air firing, oxygen firing
results in an essentially pure carbon dioxide product gas which can
be more efficiently sequestered. Most oxygen fired steam generators
utilize significant flue gas recirculation in order to maintain the
required mass flow through the steam generator to support the heat
transfer processes. Gas recirculation at high rates adds
considerable cost, complexity, and increases the need for auxiliary
power.
[0004] Typically oxygen from the air separation unit is mixed with
the recycled flue gas streams forming an oxidant stream before
entering the steam generator. There may be some limits placed on
the concentration of oxygen in the oxidant stream. For example, the
primary oxidant stream which transports pulverized fuel to the
steam generator may be limited to about the 21% oxygen content of
air to avoid problems with premature combustion of the fuel. Also
oxygen contents much above 21% may require that ducts and other
components be made of more expensive, higher grade materials
suitable for the higher oxygen content. The duct and component
limit is 23.5% for temperatures of 200-900.degree. F., which the
oxidant typically is subject to. Therefore, very good mixing of
oxygen in the recycled flue gas stream is important.
SUMMARY
[0005] According to aspects illustrated herein there is provided a
distribution and mixing grid for mixing fluids, for example, mixing
oxygen in a stream of flue gas, in a duct includes a plurality of
lances arranged in a first plane and configured to be positioned
transverse (e.g., perpendicular) to a flow direction of a first
fluid, for example, flue gas, outside of the lances and within a
predetermined flow area. Each of the plurality of lances has at
least one inlet and a plurality of outlet nozzles. One or more of
the outlet nozzles is directed generally in the flow direction of
the first fluid outside of the lances, and is configured to
discharge a second fluid (e.g., oxygen) therefrom.
[0006] According to further aspects illustrated herein, there is
disclosed an oxy-combustion system including a furnace defining an
interior combustion area, an oxygen supply system and a fuel supply
system. The fuel supply system includes a primary flue gas inlet
and a fuel outlet. The oxy-combustion system includes one or more
flue gas processing systems (e.g., an air preheater, a particulate
removal system, a sulfur removal system, a flue gas cooler and or a
carbon dioxide removal system) positioned downstream of and in
communication with the furnace. The oxy-combustion system includes
a primary gas system defining a primary flue gas outlet. The
primary gas system is in communication with one or more of the flue
gas processing systems and/or the primary flue gas outlet is in
fluid communication with the fuel inlet. The oxy-combustion system
includes a secondary gas system in communication with one or more
of the flue gas processing systems and the furnace. One or more of
the oxygen discharge lines are in communication with the primary
gas system and/or the secondary gas system. The oxy-combustion
system includes a grid positioned in a duct of the primary gas
system and/or the secondary gas system. The grid includes a
plurality of lances arranged in a first plane and positioned
transverse (e.g., perpendicular) to a flow direction of a flue gas
outside of the lances and within a predetermined flow area. Each of
the plurality of lances has at least one oxygen inlet and a
plurality of outlet nozzles. The oxygen inlet is in communication
with the oxygen supply system. One or more of the outlet nozzles is
directed generally in the direction of the flue gas flowing outside
of the lances, and are configured to discharge oxygen
therefrom.
[0007] The above described and other features are exemplified by
the following figures and in the detailed description
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] Referring now to the figures, which are exemplary
embodiments, and wherein the like elements are numbered alike:
[0009] FIG. 1 is a schematic drawing of the oxy-combustion
disclosed herein;
[0010] FIG. 2 is a perspective view of the fluid distribution and
mixing grid disclosed herein, positioned in a duct;
[0011] FIG. 3 is a graph of coefficient of variation as a function
of distance from the fluid distribution and mixing grid of FIG.
2;
[0012] FIG. 4 is a top view of lances of the fluid distribution and
mixing grid of FIG. 2;
[0013] FIG. 5 is a side elevation view of a portion of one of the
lances of FIG. 2;
[0014] FIG. 6 is a front elevation view of the fluid distribution
and mixing grid of FIG. 2;
[0015] FIG. 7A is graph showing oxygen concentration in the
recirculated flue gas at one duct diameter downstream of the fluid
distribution and mixing grid of FIG. 2;
[0016] FIG. 7B is graph showing oxygen concentration in the
recirculated flue gas at two duct diameters downstream of the fluid
distribution and mixing grid of FIG. 2; and
[0017] FIG. 7C is graph showing oxygen concentration in the
recirculated flue gas at three duct diameters downstream of the
fluid distribution and mixing grid of FIG. 2.
DETAILED DESCRIPTION
[0018] Referring to FIG. 1 an oxy-combustion system 100 includes an
oxy-combustion furnace 110, for example a tangential fired furnace.
The oxy-combustion furnace 110 includes a duct system 112, for
example, a windbox positioned at the corners of a combustion
portion 114 of the furnace and in communication with an interior
combustion area 115 of the oxy-combustion furnace 110. The
oxy-combustion furnace 110 includes an exhaust section 116
positioned downstream of the interior combustion area 115, for
exhausting flue gas from the oxy-combustion furnace 110. The
oxy-combustion furnace 110 includes an air pre-heater 120, for
example a regenerative air pre-heater positioned downstream of and
in communication with the exhaust section 116 via an outlet duct
118. The air preheater 120 defines a first side 120A, for example a
flue gas cooling side, separated from a second and third side 120B
and 120C, for example a flue gas heating side. The oxy-combustion
furnace 110 includes a particulate removal system 130, for example
an electro-static precipitator or baghouse, positioned downstream
of the air pre-heater. The particulate removal system 130 is in
communication with the air pre-heater 120 via a gas duct 128. The
oxy-combustion furnace 110 includes a sulfur removal system 140,
for example a wet or dry flue gas desulfurization system,
positioned downstream of and in communication with the particulate
removal system 130 via a gas duct 138. The oxy-combustion furnace
110 includes a flue gas cooler 150, for example a counter current
water spray heat exchanger, positioned downstream of and in fluid
communication with the sulfur removal system 140 via gas duct 148.
The oxy-combustion furnace 110 includes a gas processing system
160, for example a carbon dioxide removal and sequestration system,
positioned downstream of and in fluid communication with the flue
gas cooler 150 via a gas duct 158. The oxy-combustion furnace 110
includes an air separation unit, for example an oxygen supply
system 170 in communication with a fuel supply system 180, for
example a coal pulverizer and is in communication with the furnace
oxy-combustion furnace 110, as described herein.
[0019] Referring to FIG. 1, the oxy-combustion furnace 110 includes
a primary gas system 200 which provides a mixture of flue gas and
oxygen to the fuel supply system 180 for conveying the fuel into
the interior combustion area 115 of the oxy-combustion furnace 110,
as described herein. The primary gas system 200 includes a primary
transport duct 222 extending from a point 222A upstream of the flue
gas heating side 120B of the air preheater 120, to another point
222AA upstream of the flue gas heating side 120B of the air
preheater 120 and to the fuel supply system 180 at a point 222B.
The primary transport duct 222 is configured for receiving and
transporting a mixture of oxygen and flue gas to the fuel supply
system 180, as described herein.
[0020] Still, referring to FIG. 1, the oxy-combustion furnace 110
includes a secondary gas system 300 which provides a mixture of
flue gas and oxygen to the into the interior combustion area 115 of
the oxy-combustion furnace 110, as described herein. The secondary
gas system 300 includes a secondary transport duct 333 extending
from a point 333A upstream of the flue gas heating side 120B of the
air preheater 120 to a point 333B in the windbox 112. The secondary
transport duct 333 is configured for receiving and transporting a
mixture of oxygen and flue gas to the interior combustion area 115,
as described herein.
[0021] The primary gas system 200 is configured to selectively
receive flue gas from the oxy-combustion system 100 via a plurality
of points, for example, 1) from a first point 201 located in the
outlet duct 118 between the oxy-combustion furnace 110 and the air
pre-heater 120, to the primary transport duct 222, via a tie line
210, the secondary transport duct 333 and another tie line 299; 2)
from a second point 202 located in the gas duct 128 between the air
pre-heater 120 and the particulate removal system 130 to the
primary transport duct 222, via a tie line 220, the secondary
transport duct 333 and the tie line 299; 3) a third point 203
located in the gas duct 138 between the particulate removal system
130 and the sulfur removal system 140 to the primary transport duct
222, via a tie line 230, the secondary transport duct 333 and the
tie line 299; 4) a fourth point 204 located in the gas duct 148
between the sulfur removal system 140 and the flue gas cooler 150
to the primary transport duct 222, via a tie line 240, the
secondary transport duct 333 and the tie line 299; and/or 5) a
fifth point 205 located in the gas duct 158 between the flue gas
cooler 150 and the gas processing system 160 to the primary
transport duct 222, via a tie line 150.
[0022] Still referring to FIG. 1, the primary transport duct 222
includes a plurality of injection points, for example a first
injection point 212 located upstream of the flue gas heating side
120B of the air pre-heater 120 and a second injection point 213
located downstream of the flue gas heating side 120B of the air
pre-heater 120. A fluid distribution and mixing grid 500A, for
example the fluid distribution and mixing grid 500 shown in FIGS. 2
and 6 is positioned in the primary transport duct 222 at the first
injection point 212. The fluid distribution and mixing grid 500A is
positioned upstream of the flue gas heating side 120B of the air
preheater 120. In one embodiment, a fluid distribution and mixing
grid 500B, for example the fluid distribution and mixing grid 500
shown in FIGS. 2 and 6 is positioned in the primary transport duct
222 at the second injection point 213. The fluid distribution and
mixing grid 500B is positioned downstream of the flue gas heating
side 120B of the air preheater 120.
[0023] The secondary gas system 300 is configured to selectively
receive flue gas from the oxy-combustion system 100 via a plurality
of points, for example, 1) from a first point 201 located in the
outlet duct 118 between the oxy-combustion furnace 110 and the air
pre-heater 120 to the secondary transport duct 333, via the tie
line 210; 2) from a second point 202 located in the gas duct 128
between the air pre-heater 120 and the particulate removal system
130 to the secondary transport duct 333, via the tie line 220; 3) a
third point 203 located in the gas duct 138 between the particulate
removal system 130 and the sulfur removal system 140 to the
secondary transport duct 333, via the tie line 230; 4) a fourth
point 204 located in the gas duct 148 between the sulfur removal
system 140 and the flue gas cooler 150 to the secondary transport
duct 333, via the tie line 240; and/or 5) a fifth point 205 located
in the gas duct 158 between the flue gas cooler 150 and the gas
processing system 160 via tie line 250.
[0024] Still referring to FIG. 1, the secondary transport duct 333
includes a plurality of injection ports, for example a first
injection point 301 located upstream of the flue gas heating side
120B of the air pre-heater 120 and a second injection point 302
located downstream of the flue gas heating side 120B of the air
pre-heater 120. A fluid distribution and mixing grid 500C, for
example the fluid distribution and mixing grid 500 shown in FIGS. 2
and 6 is positioned in the secondary transport duct 333 at the
first injection point 301. The fluid distribution and mixing grid
500C is positioned upstream of the flue gas heating side 120B of
the air preheater 120. In one embodiment, a fluid distribution and
mixing grid 500D, for example the fluid distribution and mixing
grid 500 shown in FIGS. 2 and 6 is positioned in the secondary
transport duct 333 at the second injection point 302. The fluid
distribution and mixing grid 500D is positioned downstream of the
flue gas heating side 120B of the air preheater 120.
[0025] Referring to FIGS. 2 and 6, the fluid distribution and
mixing grid 500 includes a plurality of lances 510A and 510B, for
example, seven upper lances 510A and seven bottom lances 510B (FIG.
2) or ten upper lances 510A and ten bottom lances 510B (FIG. 6),
positioned in the primary transport duct 222 and/or the secondary
transport duct 333. While seven and/or ten upper lances 510A and/or
bottom lances 510B are shown and described, the present disclosure
is not limited in this regard as any number of lances may be
employed and installed in configurations other than upper and
lower, including but not limited to lances mounted through sides S
of any ducts.
[0026] Each of the upper lances 510A and the bottom lances 510B
have a plurality of nozzles formed therein for distribution of a
gas, such as, oxygen therefrom, as described below. As shown best
in FIG. 2 the primary transport duct 222 and/or the secondary
transport duct 333 have a square cross section with sides having a
length of D and a flow area defined by D.sup.2. Although the cross
section of the primary transport duct 222 and/or the secondary
transport duct 333 are shown and described as being square, the
present disclosure is not limited in this regard as any suitable
geometric cross section including but not limited to rectangular
and circular cross sections may be employed. The upper lances 510A
and the bottom lances 510B are arranged in a common plane in the
flow area and are substantially parallel to one another. The common
plane is generally transverse to, for example perpendicular to, a
direction F of flow of flue gas in the primary transport duct 222
and/or the secondary transport duct 333. While the common plane is
described as being perpendicular to the direction f of flow flue
gas, the present disclosure is not limited in this regard as other
configurations may be employed, including but not limited to any
angle relative to the direction F and in any orientation including
horizontal and diagonal. The upper lances 510A penetrate a top
portion T of the primary transport duct 222 and/or the secondary
transport duct 333. The bottom lances 510B penetrate a bottom
portion B of the primary transport duct 222 and/or the secondary
transport duct 333. The upper lances 510A define an inlet 511A and
a closed end 512A. The bottom lances 510B define an inlet 511B and
a closed end 512B. The closed ends 512A of the upper lances are
spaced apart from the respective closed end 512B of the bottom
lances 510B. As shown in FIG. 6, a sleeve 520 is positioned around
each adjacent pair of the closed ends 512A and the closed ends
512B, for support purposes. Each pair of the closed ends 510A and
the closed ends 501B are moveably positioned in the respective
sleeve 520 to allow for thermal expansion and contraction and
vibratory movement of the upper lances 510A and the bottom lances
510B.
[0027] As shown in FIG. 6, two flow control devices, for example a
control valve 522 and an orifice 524 are positioned upstream of
each of the inlets 511A and 511B for controlling the flow of a gas
such as oxygen into the upper lances 510A and the bottom lances
510B. Each of the control valves 522 is in communication with a
control system such as manual independent adjustment of the control
valves 522 and/or a controller 525, for example two controllers 525
are shown, via a line 526. The controllers 525 are in communication
with a computer processor 528 via a line 527 for, controlling the
control valves 522 and the flow of gas to the upper and lower
lances 510A and 510B, respectively. The control system, adjusts the
control valves 522 for modulating the flow of gas to each of the
lances 510A and 510B.
[0028] As shown in FIGS. 1 and 6, the oxygen supply system 170 is
in communication with each of the distribution and mixing grids
500, (e.g., 500A, 500B, 500C and 500D). As best shown in FIG. 6,
the oxygen supply system 170 is in communication with each of the
inlets 511A and 511B of the upper lances 510A and the bottom lances
510B, respectively, via the respective orifices 524 and the
respective control valves 522. While the oxygen supply system 170
is shown and described as being in communication with each of the
inlets 511A and 511B of the upper lances 510A and the bottom lances
510B, the present disclosure is not limited in this regard as one
or more fluids other than or in addition to oxygen may be supplied
to one or more of the upper lances 510A and the bottom lances 510B,
including but not limited to flue gas, air, water, steam and
sorbents.
[0029] As shown in FIGS. 2 and 4-6, each of the upper lances 510A
and the bottom lances 510B includes a plurality of nozzles 555
formed therein. In one embodiment, the nozzles 555 are holes
drilled through a surface of the upper lance 510A and the bottom
lances 510B. As best shown in FIGS. 4 and 5, there are three
nozzles 555 formed in the upper lances 510A and the bottom lances
510B, at each of a plurality of common axial locations. For
example, the upper lances 510A and the bottom lances 510B include a
central nozzle 555C aligned coaxially with the direction F of the
flue gas flow through the primary transport duct 222 and/or the
secondary transport duct 333. The upper lances 510A and the bottom
lances 510B include a first side nozzle 555A and a second side
nozzle 555B positioned on opposing sides of the central nozzle 555C
and at an angle K1 therefrom. In one embodiment, the angle K1 is
about 45 degrees, plus or minus fifteen degrees (i.e., about 30 to
60 degrees). The upper lances 510A and bottom lances 510B adjacent
to the side walls S have one of the side nozzles 555T positioned at
an angle K2 from the central nozzle 555C and spaced apart therefrom
by an angle K2. In one embodiment, the angle K2 is about 22.5
degrees, plus or minus ten degrees (i.e., about 12.5 to about 32.5
degrees). While the groups of three of the side nozzles 555A and
555B and the central nozzle 555C are shown and described as being
in a common axial plane, the present disclosure is not limited in
this regard as the side nozzles 555A and 555B may be staggered
axially from the central nozzle 555C as shown for example in two of
the lances 510A and two of the lances 510B, in FIG. 6 as referred
to by the arrow Q.
[0030] The inventors used computational fluid dynamic (CFD)
modeling and analysis to determine the quality of the mixing of
oxygen and flue gas in ducts using many configurations of one or
more static mixing grids modeled in one or more locations (e.g.,
multiple rows) in various flue duct configurations. While the CFD
modeling was performed to quantify the mixing of oxygen in flue
gas, the CFD modeling results are also applicable to the mixing of
other fluids, gases, liquids, particulate solids and combinations
thereof, such as but not limited to SO.sub.2, SO.sub.3 and
mercury.
[0031] After modeling and analyzing CFD results for a significant
number of configurations, the inventors surprisingly determined
that the grid 500 demonstrated superior mixing compared to other
configurations. For example, the CFD results for the grid 500 were
unexpected because one skilled in the relevant art would have be
discouraged from positioning a plurality of the lances 510A and
510B in a single plane, for example transverse to (e.g.,
perpendicular) to the flue gas flowing there around, because of the
increase in pressure drop of the flue gas in the duct caused by the
obstruction of the grid 500.
[0032] Mixing results for the grid 500 are presented as a
coefficient of variation (CoV), which is a measure of the mixed gas
homogeneity and equal to the standard deviation divided by the
normalized average oxygen concentration at a particular location in
the duct. CoV was determined for various lengths downstream of the
grid 500. Length was normalized and presented in terms of diameters
of duct, for example the duct equivalent diameters (L/D). A CoV of
0.05 is considered good mixing and 0.02 is considered excellent
mixing. The results of the CFD modeling are shown in FIG. 3, in a
graph of CoV versus L/D. FIG. 3 demonstrates that a CoV of 0.05 is
reached at point less than one L/D (duct diameter) downstream of
the grid 500; and that a CoV of 0.02 is reached at a point less
than four L/D downstream from the grid 500. In particular, the
graph of FIG. 3 yielded the following data points.
TABLE-US-00001 TABLE 1 CoV L/D 0.05 0.75 0.033 1.25 0.028 1.8 0.021
3.2 0.02 3.75 0.018 4.4 0.016 5.0
[0033] FIGS. 7A, 7B and 7C graphically illustrate and Table 2
summarizes the mixing performance of the grid 500 obtained from the
CFD modeling, at three distances from the grid 500, namely L/D 1, 2
and 3, respectively, for the mixing of oxygen gas injected via the
grid 500 into a flue gas stream. While the CFD modeling is
described as being for the mixing of oxygen injected into flue gas,
the modeling results also apply to the mixing of other fluids such
as gases and liquids into one another, as well as to gasses and
fluids having particulate matter entrained therein.
[0034] As shown in FIG. 7A, at a distance L/D of 1 from the grid
500, there are four corner regions A1-A4 of low oxygen
concentration, namely less than 21% (weight percent) oxygen in the
flue gas stream and eight central regions A5-A12 of low oxygen
concentration, namely less than 21% (weight percent) oxygen
concentration. The regions of low oxygen concentration occupy less
than 21% of the total flow area of the duct at a plane located at
one L/D from the grid 500. As shown in FIG. 7A, at a distance L/D
of 1 from the grid 500, there are twelve regions (B1-B12) of high
oxygen concentration, namely greater than 23.5% (weight percent)
oxygen. The regions of high oxygen concentration occupy less than
22% of the total flow area of the duct at a plane located a one L/D
from the grid 500. The remainder (i.e., greater than 57%) of the
gas has an oxygen concentration within the desired target range of
21% to 23.5% (weight percent) oxygen.
[0035] As shown in FIG. 7B, at a distance L/D of 2 from the grid
500, there are two central regions A1-A2 of low oxygen
concentration, namely less than 21% (weight percent) oxygen in the
flue gas stream. The regions A1 and A2 of low oxygen concentration
occupy less than 10% of the total flow area of the duct at a plane
located at two L/D's from the grid 500. As shown in FIG. 7B, at a
distance L/D of 2 from the grid 500, there are six regions (B1-B6)
of high oxygen concentration, namely greater than 23.5% (weight
percent) oxygen. The regions B1-B6 of high oxygen concentration
occupy less than 1% of the total flow area of the duct at a plane
located a two L/D from the grid 500. The remainder (i.e., greater
than 89%) of the gas has an oxygen concentration within the desired
target range of 21% to 23.5% (weight percent) oxygen.
[0036] As illustrated in FIG. 7C, at a distance of three L/D from
the grid 500 greater than 99% e.g., 100% of the gas has an oxygen
concentration within the desired target range of 21% to 23.5%
(weight percent) oxygen.
TABLE-US-00002 TABLE 2 Low Oxygen High Oxygen Concentration
Concentration Target Range of Oxygen Regions (oxygen Regions
(oxygen Concentration (oxygen concentration less concentration
concentration in the than 21%) greater than 23.5%) range of 21% to
23.5%) Percent Percent Percent of Duct of Duct of Duct Flow Flow
Flow L/D FIG. Designation Area Designation Area Designation Area 1
7A Corners - Less B1-B12 Less White Remainder, A1, A2, A3 than than
background Greater & A4 21% 22% area than 57% Central - A5-A12
2 7B Central - Less B1-B6 Less White Remainder, A1-A2 than than 1%
background Greater 10% area than 89% 3 7C None 0% None 0% White
Greater background than 99%, area e.g., 100%
[0037] While the present invention has been described with
reference to various exemplary embodiments, it will be understood
by those skilled in the art that various changes may be made and
equivalents may be substituted for elements thereof without
departing from the scope of the invention. In addition, many
modifications may be made to adapt a particular situation or
material to the teachings of the invention without departing from
the essential scope thereof. Therefore, it is intended that the
invention not be limited to the particular embodiment disclosed as
the best mode contemplated for carrying out this invention, but
that the invention will include all embodiments falling within the
scope of the appended claims.
* * * * *